The present invention relates to a multilayer hose for transporting hot fluids, and in particular for transporting hot water.
In the field of transporting hot water, hoses are known that are made in conventional manner of thermoplastic material such as polyvinyl chloride. The polyvinyl chloride used is a standard polyvinyl chloride giving a mean k-value of about 70. Such hoses are well suited to transporting hot water whose temperature does not exceed 75xc2x0 C. and they are of food grade quality so they can be used for transporting potable water. Above that temperature, the hose tends to deform and runs the risk of bursting and/or of becoming detached from couplings. In addition, those hoses which are normally flexible tend to become hard after being used a few times at temperatures in excess of 75xc2x0 C.
For transporting fluids, and more particularly water, at temperatures higher than 75xc2x0 C., use is made of hoses made out of elastomer material. Nevertheless, that type of material suffers from the drawbacks of being relatively expensive and usually it is not of food grade quality.
Unfortunately, the water flowing in a potable water distribution network and in the pieces of equipment that are commonly connected thereto at a temperature lying in the range 5xc2x0 C. to 100xc2x0 C. on a continuous basis must also be capable of rising to a peak of 120xc2x0 C. with a maximum operating pressure of about 10 bars.
A multipurpose hose must therefore present properties enabling it to satisfy those constraints, must be of food grade quality, and must withstand the fats that are often present in the environment of hoses of that type. In addition, the hose must be of low cost.
According to the invention, a multilayer hose is provided comprising:
a flexible inner layer of polyvinyl chloride having high molecular weight;
a flexible linking layer of polyvinyl chloride having medium molecular weight;
a reinforcing structure based on plastics material fibers; and
a flexible outer layer of polyvinyl chloride having molecular weight greater than that of the linking layer.